A lithium mixed metal oxide has been used as a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium secondary battery. The lithium secondary battery has already been put into practical use as a small-sized power supply for use in portable telephones, notebook personal computers, etc., and has also been tried to be applied to a middle-sized to large-sized power supply for use in automobiles, power storage, etc.
As a method of producing a lithium mixed metal oxide, a method of calcining a mixture obtained by mixing a mixed hydroxide containing nickel and cobalt with lithium hydroxide has been proposed (for example, Patent Document 1, etc.).
Further, a method of calcining a mixture obtained by mixing a mixed hydroxide containing nickel, cobalt and manganese with lithium hydroxide has also been proposed (for example, Patent Document 2, etc.).
As a conventional lithium mixed metal oxide, Patent Document 3 has disclosed a lithium mixed metal oxide having an average particle diameter of 0.17 μm in primary particles, a BET specific surface area of 4.67 m2/g, and a median diameter of 11 μm in secondary particles, and being represented by the formula Li1.05Ni0.45Mn0.45CO0.10O2. This lithium mixed metal oxide is obtained by a method in which a slurry containing Ni(OH)2, Mn304 and Co(OH)2 is spray-dried to obtain a granulated powder, the granulated powder and an LiOH powder are mixed to obtain a mixture, and then the mixture is calcined.